I noticed that in the bathroom, especially around the tub, these black spots are appearing between the tiles. I tried using straight bleach but they won't go away completely. What's the most effective method without damaging the grout?
I had the same problem at home and pure bleach is actually too aggressive and often doesn't work. What works better is making a paste with baking soda and hydrogen peroxide, scrubbing it really well with a hard-bristled brush along the grout lines and letting it sit for about twenty minutes before rinsing: the mold comes right off without damaging the grout. If it's really stubborn, you can add a bit of white vinegar to the mixture, but the key is using a tool that isn't too invasive and being patient about letting the product do its thing.
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